Apparatus for determining liquid levels



Feb. 17, 1953 R. R. JOHNSON 2,623,500

APPARATUS FOR DETERMINING LIQUID LEVELS Filed Sept. 16, 1948 4 Sheets-Sheet 1 FIGL-i Russell R.q]cbnson Era/anteribg l l) 7W6tbborneg Feb. 17, 1953 R. R. JOHNSON 2,628,500

APPARATUS FOR DETERMINING LIQUID LEVELS Filed Sept. 16, 1948 4 Sheets-Sheet 2 iOb- Russell 2.Johm5or2 Saverztor b 30, 7 abhor-neg- Feb. 17, 1953 R. R. JOHNSON 2,628,500

APPARATUS FOR DETERMINING LIQUID LEVELS Filed Sept. 16, 1948 4 Sheets-Sheet 3 Russel Z. R .doi zrzsorz :3 rzv erzbor" 5 7 Obborneg Feb. 17, 1953 R. R. JOHNSON APPARATUS FOR DETERMINING LIQUID LEVELS 4 Sheets-Sheet 4 Filed Sept. 16, 1948 FIG.4

lzusse. Z Z l2.dohnsor2 arm/enter Patented Feb. 17, 1953 APPARATUS FOR DETERMINING LIQUID LEVELS Russell R. Johnson, Elizabeth, N. J assignor to Standard Oil Development Company, a corporation of Delaware Application September 16, 1948, Serial No. 49,621

7 Claims. 1

The present invention relates to a means for determining fluid levels. More particularly the invention relates to such means whereby the gravimetric pressures of one or more fluids contained in a process vessel may be utilized to provide for determination of fluid levels within the process vessel or for determination of the level of an interface between such fluids in the vessel. It is an object of the invention to provide for such determinations with reference to a fixed interface between a process fluid and a seal liquid of different specific gravity and substantially immiscible with the process fluid. Another object of the invention is to permit visual determination of fluid levels wherev the process fluid normally tends to interfere with visual inspection because of high viscosity, corrosiveness, or because of foreign matter present in the fluid.

The invention andv its objects may be, fully understood from the following specification when read in conjunction with the accompanying drawings, in which Figure 1 is a substantially diagrammatic showing of the apparatus as applied for the determination of an interface between two process fluids, the elements being shown in vertical section;

Figure 2 is a similar view of a portion of the, apparatus, according to Figure 1, illustrating. an alternate arrangement, of certain. elements;

Figur 3 is a substantially diagrammatic showing of another applicationof the invention;

Figure 4 is a similar view of. an. alternate arrangement of the apparatus as illustrated in Figure 3; and

Figure 5 is a crossesection through the seal pot along the line VV of Figure 4.

In the apparatus shown by the drawings, the numeral I indicates a portion of a process vessel containing process fluids 2 and. 3. Normally, both fluids may be liquids. of different specific gravity and substantially immiscible, one with another, being contained in the vessel I with an. interface XX between them. Under certain condtions of operation however, the fluid 2 may be gaseous in form. The numeral 2a designates an upper level for the body of fluid above the interface XX, or of a single fluid in the vessel I.

For the purpose of determining the level of the interface X-X in the process vessel I, shown in Figure 1, a pair of receiver vessels or seal pots 4 are connected into the process vessel I by means of lines 5, containing valves 5a. These pots 4 are disposed in vertically spaced relation with reference to the process vessel so that any normally anticipated variation of the level of interface XX may be contained between the T851366? tive openings of the lines 5 into the process vessel. In each of the pots I the line '5 extends through one end wall portion, as shown, the bottom end wall portion, opening into the pot in spaced relation to the wall portion through which extended.

and provided with a trap element 6 opening into the seal pot member 4. vided with a vent valve I which may be utilized for filling the pot with a seal liquid 8 of different specific gravity than the process fluids in the vessel I, and substantially immiscible withsuch fluids. Under ordinary circumstances however. the valve I will be used to relieve any undesirable accumulation of vapors or gases in the receiver or pot 4.

Opening through aside wall portion of each of the receivers or seal pots 4 at a level intermediate that of the terminal levelv of the line 5 within the pot 6, and the end wall portion throughv which said line'5 enters" the pot, are conduits 9 and it provided with valves 9a and Illa. Lines II and I2, having valved openings Ila and l2a, respectively, communicate with. conduits 9 and E53, and are normally used for th purpose of introducing the seal liquid 8. Conduit 9 communicates with the lower portion of a reservoir I3 for a manometer liquid I l, the upper portion of the reservoir I3 communicating, by means of line, I5, ith the upper end of a manometer IS. A valved line, lie is provided for filling and replenishing the manometer liquid. The reservoir I3 should be of a transparent material. or be provided with a gauge or sight glass, such as I3b, to. permit visual inspection of the interfacial level of'liquids in the reservoir. In the apparatus as shown, the manometer liquid I4 is. of lighter specific gravity than, and substantially immiscible with the seal liquid 8, but need have no specific relation in gravity or miscibility with either of the process The conduit I0 communicates. with the.

fluids. lower end of the manometer I6, and the. conduits 9 and Iii are interconnected by meansof branched lines at and Itb through a manometer balancing valve i1.

In the apparatus as illustrated, theseal liquid 8 is of higher specific gravity than either of the Under such circumstances.

process fluids 2 and 3. the fluid 2, with the valve 5a open, will fill the upper line 5 and establish an interface with the seal liquid 8 in the trap 6 wherein, along the line.

Each seal potl is pro-- ZZ. In both instances the trap member 6 is so arranged with reference to the terminal end of a line 5, that the interface level between the process fluids and the liquid 8, in the respective upper and lower seal pets, will be established at the level of the terminal ends of lines in the seal pots 4.

In commencing operation with the system as described, the valves 50. will be closed and the system drained. of all contents, as by means of drain valves ia, I30 and iilc. Iiia will then be closed, and the manometer reser voir I8 filled with a manometer liquid I4. Next, the valves 9a and Ida will be opened, as will be the balancing valve II and the system filled with seal fluid 8. The balancing valve I? will then be closed and valves 5a opened. Upon opening of the valves 5a the interface levels ZZ and Y-Y will be established in the trap elements 6 and the seal liquid 8 will seek a level in each of the manometer elements i3 and I5, depending upon the gravimetric pressures exerted by the fluids contained in the process vessel.

The interfacial level between the manometer liquid I4 and the seal liquid 8 having been established in the reservoir I3, and the manom- (Di-D.)

in which:

1. hi is the distance from the interface ZZ in the lower receiver 4, and the interface X-X in the process vessel I;

2 ha is the distance between the interface Y-Y, in upper receiver l, and the interface X--X in the process vessel I;

3. M is the distance between the interface between the manometer liquid I4.and the seal liquid 8 in manometer I6, and the interface between said liquids in the reservoir I3;

4. D1 is the density of the process liquid above the interface XX in the process vessel I;

5. D2 is the density of the process liquid below. the interface XX in the process vessel I;

6. D3 is the density of the seal liquid 8; and

7. D4 is the density of the manometer liquid Id.

In this formula the sum of the distances hr and hz is equal to the fixed and known distance between the interfacial levels YY and ZZ in the upper and lower pots 4, respectively. The distance M may be determined by measurement of the distance between the interfacial levels of the manometer and seal liquids in the manometer I6 and the reservoir I3, respectively. The densities of the respective fluids will, of course, be predetermined and known. Thus, the distance k2 being determined by calculation according to the formula may be subtracted from the total known distance between the interfaces ZZ and YY to exactly determine the level of the interface XX in process vessel I with reference to either of the interfacial levels in the seal pets 4. Variations of the interfacial level X may be similarly determined or, by precalculation of any given number of possible variations, the tube of manometer I6 may be suitably impressed or marked with indicia such that a direct reading of the interfacial level X-X may be obtained.

In the alternate arrangement illustrated by Figure 2, provision is made for the use of a manometer liquid which is heavier than the seal liquid. As shown, the reservoir I3 is connected The valves 90. and

4. to the conduit III, which enters the reservoir adjacent the upper end thereof. The line I5 in this instance opens from a lower portion of the reservoir I3, into the lower end of the manometer I6, the upper end of the manometer It being connected to the conduit 9.

In Figure 3 is illustrated an arrangement in which only the upper level of a single process fluid contained in the process vessel I is to be determined. In such a situation, a single seal pot is utilized to which is connected a manometer it, a connecting line I9 entering the pot 4 through a side wall portion, at a level intermediate that of the interface WW and the end wall portion through which the line 5 enters the pot. In this arrangement the seal liquid 8 functionsas well asthe manometer fluid, no

separate manometer liquid being used.

In general, the operation of this form of the invention is comparable to that of the apparatus illustrated by Figure 1. The seal pot A is filled by means of the valve I with a Seal liquid, in this instance, heavier than the process liquid 2, the valve 5a being closed. Upon opening the valve 5a, the head of the fluid 2 in the process vessel I will be balanced against the head of liquid in the manometer I8. As in the operation of the apparatus described with reference to Figure 1, a fixed interface will be established in the trap 6 between the process fluid 2 and the seal liquid 8. Any increase or decrease of level 2a will then; result in the imposition of a greater or lesser pressure of the process liquid upon the seal liquid. In the first instance this will result in the process fluid being forced into the seal pot 4 through the trap 6 where, being lighter than the seal liquid, it will rise to the upper portion of the pot, displacing seal liquid from the'pot into the manometer tube I8, raising the level of liquid therein. A decrease in the level 2a. of fluid 2 in the process vessel I will decrease the pressure of such fluid upon the seal 1iquid8 resulting in withdrawal of the seal liquid from the pot 4 through the trap 6 and line 5 into the process vessel 1 the liquid withdrawn being replaced in the pot '4 by liquid from the manometer tube I8, thus lowering the level of liquid in the tube. 'Under normal circumstances the introduction of the process fluid into the pot 4 or the withdrawal of seal liquid therefromwill be in very small volume, but in any event the introduction of process fluid into the pot 4 or the withdrawal of seal liquid therefrom will not affect the operation of the device until the level of the seal liquid reaches the interface WW. At that point the seal pot A should be drained and refilled with fresh seal liquid.

As in the operation previously described with reference to Figure 1, the level 2a of the fluid 2 in the process vessel I, may be determined from the level of liquid in the manometer I8 by a simple calculation based on the formula in which: v

1. in is the distance between the interface WW and the process fluid level 2a.;

2. ha is the distance between the interface W -W and the level of liquid in the manom eter I8;

3. D1 is the density of the process fluid 2; and V 4. D2 is the density of the seal liquid 8. With the interface WW fixed and known,

pressures above the fluids have a negligible differential or are equal the distances, hl and hz will be inversely proportional to the fluid gravities.

The apparatus shown by Figures 4 and 5 illustrates the arrangement of elements required when a seal liquid is used which has a lower specific gravity than the process liquid 2. Figure 4 and Figure 5 also illustrate another form of trap usable according to the present invention. In this form the trap is: a substantially semi-circular portion of a cylindrical member, indicated by the numeral 20, secured to a side wall portion of the seal pot 4 in spaced relation to one end wall portion, the space thus defined by member is being closed at one end by a cover element 26a. The line 5 is introduced through such end wall portion in close proximity to the sidewall of the pot 4 at a mid-pointof the space defined by the element I9. Preferably the line 5 is secured to the side wall of the pot' 4. As previously disclosed, the inner end of the line 5 terminates in the same plane with the open end of the element 2!], whereby in operation an interface W--W is established and between the seal liquid 8 and a process fluid 2 in such predetermined plane. the numeral 2! designates a try-cock used to determine the lower or upper limit of seal fluid in the pot A. When process fluid flows from the try-cock 2| the seal pot 4 should be refilled.

When, as illustrated in Figures 4 and 5, a seal liquid is used which is of lower specific gravity than the process fluid, the seal pot must be inverted as shown. Under such circumstances the trap element is disposed adjacent to and in spaced relation to the upper end wall portion of the seal port t with the line 5 entering through such upper end wall portion and the manometer I8 opening into the seal pot adjacent the upper end above the trap and extending upwardly therefrom. In all other respects the construction and operation of the apparatus remains the same as described with reference to Figure 3.

A principal advantage of the present invention lies in the provision of a fixed and known level for the interface betweeen a process liquid and a manometer or seal liquid in the seal pot element A, which level may be used as a reference point for measurement of a process fluid level under any circumstances of operation. For example, in the apparatus as shown by Figure 1, if the process fluids are phenol or oil, a change of one inch in the level of the interface X--X in process vessel 1 would result in a change in differential pressure equivalent to only 0.1 inches of water. Any uncertainity or variation in the location of a reference point such as the interfaces ZZ or YY in the seal pots 4 would make it practically impossible to determine such a small variation in the interface X--X. Other uses for apparatus of the character described, include measurement of pressures in vapors which are near the dew-point where the use of a sealing system is desirable to prevent accumulation of condensate in the lines of the equipment utilized for measurement.

Various materials may be utilized as the seal liquid material 8, and also as a manometer liquid material Hi. A principal requirement in either instance is that they be clean, and of a substantially stable nature to permit visual determina- In each of Figgures 3, 4 and 5 tion. of their levels in the manometer tubes. l6- As previously stated, the seal liquid ma-. 1

and I8. terial must also be substantially immiscible with the process fluids with which it comes in. contact, and of a different specific gravity, and the manometer liquid material must have a substantially similar relationship to the seal liquid, but. not essentially with reference to the. process fluids. i

In the operation set forth with reference'to Figure 1, for example, the seal liquid may be a. silicone oil, particularly one known as DC710,

having a specific gravity of 1.11 at 25 C;, and which is an organo-silicon oxide polymer. In

such case the manometer liquid may be water,

be glycerine, preferably dyed, or mercury may be substituted for a true liquid. A silicone oil may also be employed in the apparatus according to the other drawings, provided that the process fluid is substantially immiscible therewith, andof higher or lower specific gravity.

What is claimed is:

1. Apparatus for indicating the level of a process fluid in a process vessel, comprising a closed receiver for a seal liquid substantially immiscible with the process fluid, and of different specific gravity, a body of seal liquid in said receiver, a conduit having an open terminal end disposed at a predetermined level within the receiver, extending outwardly through an end wall thereof into communication with a process fluid in said vessel, a trap shield element having a closed end and an open end facing the terminal end of said conduit, with said conduit terminal end and the open end of said shield element disposed in the same plane and thereby establishing a fixed interface between the seal liquid and the process fluid, and manometer means indicating the gravimetric pressure of process fluid in the vessel above said interface upon the seal liquid communicating with said receiver through a side wall thereof at a level between that of the terminal end of the conduit and the end wall of the receiver through which said conduit is extended outwardly.

2. Apparatus according to claim 1, in which the seal liquid is of higher specific gravity than the process fluid with which said conduit and receiver are in communication, said conduit extending outwardly through the lower end wall of the receiver.

3. Apparatus according to claim 1, in which the seal liquid is of lower specific gravity than the process fluid with which said conduit and receiver are in communication, said conduit extending outwardly through the upper end wall of the receiver.

4. Apparatus for indicating the interfacial level between two substantially immiscible process fluids in a process vessel, comprising a pair of closed receivers for a seal liquid substantially immiscible with either process fluid and of different specific gravity, dispose-d in spaced relation vertically of the process vessel, a conduit having an open terminal end disposed at a predetermined level within the upper receiver, extending outwardly through an end wall thereof into communication with a process fluid in the upper portion of said vessel, a similar conduit similarly disposed and connecting the lower receiver with a process fluid in the lower portion of said vessel, trap shield elements each having a closed end and an open end facing over a terminal end of one of said conduits within each receiver, each conduit terminal end and the open end of a shield element disposed in the same plane and thereby establishing a fixed interface between the respective process fluids and the seal liquid in each receiver, and manometer means integrating the gravimetric pressures exerted at the respective interfaces established within each of said receivers, connectedand in communication at one end with the upper receiver, and at the other end with the lower receiver at levels between those of the terminal ends of said conduits in the respective receivers, and the end walls thereof through which said conduits are extended outwardly.

5. Apparatus according to claim 4, in which said manometer means comprises a reservoir for a manometer liquid immiscible with the 'seal liquid and of different specific gravity, said reservoir communicating at one end with a seal liquid receiver, and at the other end to a manometer tube, the other end of said manometer tube in communication with the other receiver for seal liquid.

6. Apparatus according to ,claim 5, in which 8 said manometer liquid is of lower specific gravity than the seal liquid, and said reservoir is connected between the upper end of the manometer tube and the upper receiver for seal liquid.

7. Apparatus according to claim 5, in which said manometer liquid is of higher specific gravity than the seal liquid, and said reservoir is connected between the lower end of the manometer tube and the lower receiver for seal liquid;

' RUSSELL R. JOHNSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 337,910 Wilcox Mar. 16, 1886 1,466,359 Field Aug. 28, 1923 1,567,758 Schriever Dec. 29, 1925 1,733,616 McNeil Oct. 29, 1929 1,902,276 Bull Mar. 21, 1933 2,158,785 Hall 1 Ma 16, 1939 2,187,210 McDonald Jan. 16, 1940 2,525,807 Lane Oct. 17, 1950 

